An organic electrophotographic photosensitive member (hereinafter, referred to as “electrophotographic photosensitive member”) containing an organic charge-generating substance (organic photoconductive substance) is known as an electrophotographic photosensitive member mounted on an electrophotographic apparatus. In an electrophotographic process, a variety of members such as a developer, a charging member, a cleaning blade, paper, and a transferring member (hereinafter, also referred to as “contact members or the like”) have contact with the surface of the electrophotographic photosensitive member. Therefore, the electrophotographic photosensitive member is required to reduce generation of image deterioration due to contact stress with such contact members or the like. In particular, in recent years, the electrophotographic photosensitive member is required to have a sustained effect of reducing the image deterioration due to contact stress with improvement of durability of the electrophotographic photosensitive member.
For sustained reduction of contact stress, Patent Literature 1 has proposed a method of forming a matrix-domain structure in the surface layer using a siloxane resin obtained by integrating a siloxane structure into a molecular chain. In particular, the literature shows that use of a polyester resin integrated with a specific siloxane structure can achieve an excellent balance between sustained reduction of contact stress and potential stability (suppression of variation) in repeated use of the electrophotographic photosensitive member.
On the other hand, there has been proposed a technology for adding a siloxane-modified resin having a siloxane structure in its molecular chain to a surface layer of an electrophotographic photosensitive member. Patent Literature 2 and Patent Literature 3 have each proposed an electrophotographic photosensitive member containing a polycarbonate resin integrated with a siloxane structure having a specific structure, and effects such as contamination prevention and filming prevention caused by releasing effect have been reported.
The electrophotographic photosensitive member disclosed in Patent Literature 1 has an excellent balance between sustained reduction of contact stress and potential stability in repeated use. However, the inventors of the present invention have made studies, and as a result, the inventors have found that, in the case of using a charge-transporting substance having a specific structure as a charge-transporting substance, the potential stability in repeated use can further be improved.
In the electrophotographic photosensitive member including a surface layer containing a siloxane-modified resin having a siloxane structure in its molecular chain, disclosed in each of Patent Literature 2 and Patent Literature 3, a balance between sustained reduction of contact stress and potential stability in repeated use cannot be achieved.